"Extinction" is the fifty-fifth episode of the American science fiction television series Star Trek: Enterprise, the third episode of season three. It first aired on September 24, 2003, on the UPN network in the United States. This was the first episode following the addition of the prefix "Star Trek" to the title of the series. Set in the 22nd century, the series follows the adventures of the first Starfleet starship, Enterprise, registration NX-01.